Unveiling Critical Role of Metal Oxide Infiltration in Controlling the Surface Oxygen Exchange Activity and Polarization of SrTi1-xFexO3-δ Perovskite Oxide Electrodes

Enhancing the oxygen reduction activity of mixed electronic-ionic conducting oxides holds paramount importance in various energy and fuel conversion technologies. One effective method has involved manipulating surface oxygen kinetics on fluorite-type oxides via controlled acidity of infiltrated binary oxides. This strategy is now extended to the commercially utilized but more complex perovskite-oxide-based electrocatalysts by investigating the impact of surface infiltration of basic CaO or acidic Al2O3 on the oxygen exchange kinetics of perovskite structured SrTi1-xFexO3-δ (STFx) mixed conductors. By systematically assessing the degree of activation or deactivation induced by infiltration on STFx as a function of iron concentration x, we validate the applicability of the acid-base approach as well to perovskite oxides. A straightforward infiltration of CaO into STFx with the lowest iron content increased the surface oxygen exchange rate by approximately 40-fold and reduced electrode polarization by 35%. Despite the fact that the surface oxygen exchange rate of uninfiltrated specimens exhibits a divergence of over an order of magnitude, increasing with increases in x, it tends to converge following CaO or Al2O3 infiltration. This highlights the opportunity of utilizing infiltrated STFx with low iron content, offering significantly improved mechanical, thermal, and chemical stability.